Sunday, June 10, 2007

More mammoth news

We have another new study that weighs in on the mystery of mammoth extinction this week. I wish this story had come out about four days earlier so I could have included it in my last big mammoth post. Just in case you were laying awake at nights wondering if the entire world was organized for John's convenience, this is a vote in the "NO" column. Sigh.

Some ancient-DNA evidence has offered new clues to a very cold case: the disappearance of the last woolly mammoths, one of the most iconic of all Ice Age giants, according to a recent article.

Get it: "cold case, Ice Age?" These folks are clearly crowding in on my act.

DNA lifted from the bones, teeth, and tusks of the extinct mammoths revealed a "genetic signature" of a range expansion after the last interglacial period. After the mammoths' migration, the population apparently leveled off, and one of two lineages died out.

"In combination with the results on other species, a picture is emerging of extinction not as a sudden event at the end of the last ice age, but as a piecemeal process over tens of thousands of years involving progressive loss of genetic diversity," said Dr. Ian Barnes, of Royal Holloway, University of London. "For the mammoth, this seems much more likely to have been driven by environmental rather than human causes, even if humans might have been responsible for killing off the small, terminal populations that were left."

Besides its intrinsic interest, the end ice age extinctions are important to paleontologists for the simple reason that we have more information about this extinction event than any other. Both because it was so recent and because we are still in the Pleistocene Ice Epoch, many of the extinct animal remains that we have to examine are not yey fossilized. We have actual soft tissue of hair, skin, bone marrow, internal organs, and, most importantly, we have DNA. We know more about mammoths than any extinct animal outside those that we are currently in the process of driving extinct.

This sort of genetic diversity study is an example of the kind of work that we can do on the end ice age extinction event that we can't do on, for example, the much more popular K-T event which killed the dinosaurs. Because we can study this kind of detail about this event, it has a special importance as a test case for any broad generalization that anyone makes about extinction.

This study has an impressive list of co-authors, including Adrian Lister of the University College London and the Natural History Museum in London, a major authority on things mammothy, and R. Dale Guthrie University of Alaska in Fairbanks, the primary spokesman for the climate model of end ice age extinctions. In the name of full disclosure (or bragging), my number one sister works for the University of Alaska system and has participated on an important dig with Prof. Guthrie.

A limitation to this study is that it primarily focussed on Siberian mammoths (the region from whence we get most of our best mammoth remains). Any conclusions they draw must be qualified by that limitation. However, like the Kennett study and the Last study, this sort of work piecing together the regional details of the transition from the last ice age into the current interglacial is relevant today in understanding major climate change and especially exciting to me, just because.